Electric switch



June 13, 1939. l. E. M CABE ELECTRIC SWITCH Filed Feb. 10, 1937 INVENTORIRA E. MCABE BYK A TTORNE Y.

Patented June 13, 1939 UNITED STATES PATENT OFFICE memo swrrcn Ira E.McCabe, Chicago, Ill. Application February 10, 1931, Serial No. 124,982

15 Claims. (01. zoo-13s This invention relates to improvements inelectric switches, and more particularly to a switch so constructedthat, while unaffected by changes in ambient temperature, it isresponsive to the action of radiant energy emanating from a. source oflight to open or close, and is a further development or continuation ofthe invention disclosed in the applicant's prior copending applicationSerial No. 94,352, filed August5, 1936.

It is an object to provide a. switch of the character described with asingle thermal actuating element so constructed as to be unaflected byambient temperature, and to provide means for concentrating the rays oflight upon a portion of the thermal element.

The advantages of this improved construction over that disclosed in saidprior copending application are obvious. The mass of material in thethermal element is reduced to a minimum and thereby reduces the amountof radiant energy required to operate the switch. When employed as apart of a fluid fuel burning device, the switch may be focused upon abright spot of the flame and be unaffected by normal fluctuation in theflame. Also, the rays of light emanating from sources other than thatupon which the switch is focused will be deflected from the thermalelement.

With these and other objects in view reference is made to theaccompanying sheet of drawings which illustrates preferred embodimentsof this invention, with the understanding that minor changes may be madewithout departing from the scope thereof.

85 In the drawing:

Figure 1 is a view in side elevation of one form of this improved switchwith parts broken away and partly 'in section.

Figure 2 is an enlarged view in transverse ver- 40 tlcal section takenon the line 2-2, Figure 1,

looking in the direction of the arrow.

Figure 3 is an enlarged detail view of the operating members of Figure 1shown partly in top plan and partly in section.

Figure 4 is a view similar to Figure 2 of another form of thisinvention.

Figure 5 is an enlarged expanded detail fragmentary view of one form ofthermal member.

Figure 6 is a similar view of another form of thermal member.

Figure 7 is a schematic view showing the wiring diagram of an oil burnercontrol employing this improved switch.

Figure 8 is a view in vertical central section of another form of thisinvention, with parts shown in elevation.

Figure 9 is a detail plan view of a modifled form of coiled thermalmember.

The preferred form of this improved switch is 5 shown in Figures 1, 2, 3and 'l and includes a sealed container l preferably of glass having awell 2 at the unobstructed end thereof and two electrodes 3 and 4 sealedin the opposite end thereof. The electrode 3 is arranged to nor- 10mally enter and remain in contact with a glcbule of mercury 5 or otherelectrical conducting fluid contained in the well 2 when the switch isin the position shown in Figure 1. The electrode I is so formed that itsfree end extends in the axis 15 of the container l, as shown in Figure3, and mounts thereon a concave reflector 8 and by an extension 1 fromthe free end a coiled thermal member 8, the termination of the outerconvolution thereof carries a contact piece 9 adapted to 20 be engagedand withdrawn from the mercury 5 to make and break the circuit throughthe switch.

The thermal member 8 is in the form of a coil of bi-metallic or thermalmetal, and, as shown in Figure 5, is so constructed that at approxi- 25mately the middle of the coil the metals I 0 and II are relativelyreversed, so that when subjected to changes in ambient temperature onesection of the coil expands while the other section contracts, with theresult that since the 30 inner convolution of the coil is secured uponthe stationary or immovable extension I the relative position of thecontact 9 upon the free end of the outer convolution remains unaffectedby changes in ambient temperature. If desired to prevent the heatabsorbed in one section being transmitted to the adjacent section,material I 2 of low heat transmission may be inserted between the twosections as shown in Figure 6.

The extension I from the electrode 4 supports the thermal coil I axiallyof the end of said electrode and of the container I with the entireinner section of the coil, before the change in the relations of thebi-metallic metals l0 and II, supported within the fleld of the raysreflected from the concave reflector 8. as shown in Figure 3. When theaxis of the container l is in line with a source of light, the directrays strike the entire surface of the coil 0 adjacent the source. sothat one section will expand and the other contract as when affected bychanges in ambient temperature with no operation of the switch. but therays reflected by the concave reflector 6 upon the side of the coil Imost distant from the source of light are concentrated upon theinnermost section of the coil 8 and will cause the coil to expand orcontract in accordance with the 'nature of the thermal material employedto open or close the circuit by the movement imparted to the contact 9.In the construction shown in Figures 1, 2 and 3, the coil 8 is soconstructed as to expand and open the circuit as a result of thepresence of a source of light when aligned therewith. Should a source oflight be estabiished at an angle to the axis of the container I, suchrays will not be concentrated upon the inner section of the coil butwill be reflected by the concave reflector 8 either upon both sectionswith the same result as changes in ambient tem- 'perature or so as notto fall upon the coil.

In the switch shown in Figure 4, the contact 9 normally closes thecircuit. The coil 8 is constructed as above described, but the sectionsemploy metals offering different resistance to the passage of theelectric current, whereby the continued passage of an electric currentwill cause a greater increase in temperature in the outer section of thecoil to open the switch. The presence of a source of light in line withthe axis of the container l before the opening of the circuit willconcentrate the rays from the concave redoctor 6 upon the inner sectionof the coil to increase its temperature to that of the outer section andthe circuit will continue to pass through the switch. If desired, anexternal magnetic force M may be employed to enact with an armature ofmagnetic metal l mounted upon the contact 9 so positioned that upon theopening of the switch the armature I0 is brought within the field of themagnetic force M and the resistance of the magnetic force must beovercome before the switch will close, so that the normal closing of theswitch will be prevented, thereby necessitating a manual resetting suchas the removal momentarily of the magnetic force M from the armature ID.

A practical application of this improved switch is illustrated in Figure'7 wherein a commercial form of the pressure type of oil burner O isshown installed with a commercial type of a domestic heating furnace Fwith the electrical control connection shown in diagram. The relay R,main switch MS and safety switch SS are preferably constructed andoperated as disclosed in this applicant's prior Patent No. 2,024,697,dated December 1'7, 1935. When the burner O is idle the circuit from thecommercial source is completed from wire L through the commercial boilercontrol B, safety switch SS and primary windings of the relay R to wireL. When the room: thermostat T, a commercial article, closes the circuitthrough the secondary winding of the relay R, it not only operates therelay to close the main switch MS to the burner motor, but it alsocloses the circuit through the heating element H of the safety switch,which will at the end of a predetermined time open the safety switchunless this part of the circuit is shunted out.

The form of this improved switch illustrated-in Figures 1, 2 and 3 isshown mounted in the draft pipe P of the oil burner with the axis of itscontainer l in line with the burner flame and the switch is shownconnected in the secondary circuit to shunt out the safety switch if theburner fluid is ignited within the said predetermined time. The switchin container I is normally open so that when the room thermostat T callsfor heat by closing, the establishment of the burner flame creates asource of light which acts upon the improved switch to close its circuitand Shunt the heating element as long as the flame burns. The increaseor decrease of ambient temperature within the draft pipe P within whichthe switch I is mounted does not affect its operation.

The form of this improved switch illustrated in Figure 4 is a furtherdevelopment of the employment of operating members oil'ering differentelectrical resistance to the passage of an electric currenttherethrough, as disclosed in this applicants prior co-pendingapplication executed Decamber 30, 1936, Serial No. 118,719, flledJanuary 2, 1937.

It is to be understood that in the form shown in Figure 2 while thethermal operating coil 8 includes two continuous sections, both sectionsare of material offering the same electrical resistance to the passageof an electrical current through the coil when the switch is closed butthe response of the sections is reversed upon changes in temperature,that is, one contracts while the other expands and, as this inventioncontemplates constructing each section of similar materialshaving thesame coefficient of expansion, the relation of the contact 9 to themercury 5 will not be changed until the temperature of one section ofthe thermal coil 8 is affected by a change in temperature not impartedto the other section, as by concentrating the rays of light by thereflector 6 upon the inner section, as shown in Figure 3. The thermalcoil 8 in the form shown in Figure 4 is formed of two sections ofreverse responsiveness to changes in temperature and of materials havingthe same coefficient of expansion, but as this invention contemplatesthat the normal position of the switch is closed when the circuit isclosed thereto and that the sections of the coil 8 offer differentelectrical resistance to the current passing therethrough when thecircuit is established, it is desirable to place the greater electricalresistance in the outermost section of the coil so that the passage ofthe current will-increase the temperature of the outer section to agreater degree than that of the inner section to cause the switch toopen unless the temperature of the inner section of the coil'8 iscorrespondingly increased, as by concentrating the rays of light by thereflector 6 upon the inner section.

Figure 8 illustrates the application of this invention to a differenttype of container than that shown in Figures 1 and 7. In this type ofswitch the axis of the container lies in a vertical plane when theswitch is in operative position and the rays of visible light emanatingfrom the source of light pass through the opposite walls of the bulb andare concentrated upon the thermal coil by the reflector 6a which isarranged upon the exterior of the side of the switch opposite the sourceof light. It is preferable to employ a container in which the contour ofthe bulb may be adapted to support the means for concentrating the raysof light and the reflector 6a may be a metal disc, as shown, formed tofollow the curvature of the container or consist in coating the surfaceof the bulb with paint or metal leaf to form the concave reflector 811;

It has been found that the type of heating element shown in Figure 9 maybe most advantageously employed in such a device wherein the rays ofvisible light are concentrated'thereon to normally fall upon the inneror central section of the coil. This improved coil 80 is composed of twoequal lengths of thermal metal arranged to be oppositely responsive tochanges in temperature which are joined to each other by overlapping theadjacent ends to oifset the inner convolution of the outer coil andspace it apart from theadjacent inner convolution, as shown. Thisconstruction makes the heating element more sensitive in operation anddoes not require the same precision in mounting the coil 8 shown inFigures 2, 3 and 4, because such reflected rays as may overlap the innercoil will fall in the space between the sections and not affect theouter section.

It has also been proven by actual test that coils such as 8a may beconstructed of thermal metal that in weight need not exceed oneonethousandth of an ounce. These switches, because of the small mass of,material to be afiected by the reflected rays, may be made highlysensitive and responsive to small sources of light,- such as thatemanating from a gas burner pilot flame. Furthermore, switches of thisconstruction have been found to operate satisfactorily at distances fromthe light source greater than possible with switches constructed inaccordance with the applicants prior co-pending application Serial No.94,352, filed August 5, 1936.

The use of light sensitive switches, particularly in control systems forthe automatic control of fluid fuel burners is well known to theapplicant, as will be evident from the disclosure made in his priorPatent No. 1,745,178, granted January 28, 1930, upon an applicationflied December 6, 1926.

The switch of the type shown in this aforementioned patent requires alarger space and a greater amount-of energy for operation, althoughoperating from light, than does the switch disclosed in this invention.It is also more expensive to build and more fragile than this Theadaptation of this improved switch to the applicant's previous inventionwill greatly increase its usefulness and scope.

It is also to be understood that the use of this invention is notrestricted to a fluid fuel burner control herein disclosed, as thisdisclosure is but one of many uses. It is obvious that this improvedswitch niay be employed wherever it is desirable to use a switchresponsive to radiant energy without being afl'ected by changes inambient temperature.

What I claim is:

1. A thermally actuated switch responsive to the radiant energy of lightincluding a stationary electrode, a movable electrode, a thermaloperating coil forming a part of the movable electrode for making andbreaking contactwith the flxed electrode, said operating coil beingformed in two uninterrupted continuous sections oppositely responsive totemperature changes whereby the relation between the electrodes isunaffected by changes in ambient temperature, and means forconcentrating rays of light upon one section to operate the switch.

2. The structure of claim 1 wherein the switch is mounted within atransparent container having the portion of the movable electrodesupporting the thermal coil and the thermal coil arranged axially of thecontainer.

3. The structure of claim 1 wherein the switch is mounted within atransparent container having the portion of the movable electrodesupporting the thermal coil and the thermal coil arranged axially of thecontainer, and the means for concentrating the rays of light including aconcave reflector.

4. The structure of claim 1 wherein the switch is mounted within atransparent container having the portion of the movable electrodesupporting'the thermal coil and the thermal coil arranged axially of thecontainer, and the means for concentrating the rays of light includinga. concave reflector and wherein said reflector is mounted upon theaxial portion of the movable electrode. v

5. The structure of claim 1 wherein the switch is mounted within atransparent container having the portion of the movable electrodesupporting the thermal coilv and the thermal coil arranged axially ofthe container, and the means for concentrating the rays of lightincluding a concave reflector and wherein said reflector is mounted uponthe axial portion of the movable electrode and so arranged that only onesection of the oppositely responsive thermal sections lies wholly withinthe held of the rays of light reflected by the concave reflector.

6. In a light responsive switch, an operating member therefor includinga coil of bi-metallic or-thermally responsive metal formed in twouninterrupted continuous sections which are oppositely responsive tochanges in temperature and Y each possesses the same coefllcient ofexpansion whereby the operationis unaflected by changes in ambienttemperature.

7. The structure of claim 6 wherein the sections of the coil oiferdiiferent electrical resistance to the passage of an electrical currenttherethrough, whereby upon establishment of the circuit through theswitch the section of the coil oil'ering the greatest resistance willrespond to the difference in temperature between the two sections tooperate the switch.

8. In a light responsive switch, an operating rim switchrmember thereforincluding a coil of bi-metalllc or thefmallyresponsivemetal formed intwo uninterrupted continuous sections which are oppositely responsive tochanges in temperature and each s the same coeflicient of expansionwhereby the operation is unaflected by changes in ambient temperature,wherein the sections of the coil offer different electrical resistanceto the passage of an electrical current therethrough, whereby uponestablishment of the circuit through the switch the section of the coiloffering the greatest resistance will respond to the difference intemperature between the two sections to operate the switch, and meansfor concentrating rays of light upon the section of the coil offeringthe least electrical resistance to the passage of an electrical currenttherethrough whereby its temperature is raised to equal that of theother section and cause the thermal coil to remain in'inoperativerelation to the switch.

9. The structure of claim 8 wherein said last named means includes aconcave reflector axial-- 1y arranged in relation to the thermal coiland upon the side thereof most distant from the source of light.

10. The structure of claim 8 wherein an armature is mounted upon a partof said operating means and a magnetic force arranged exterior ,of saidswitch adapted to hold said armature concave reflector supported uponthe electrode carrying the thermal coil.

14. The structure of claim 11 wherein the means to concentrate the raysof light includes a concave reflector supported exteriorly of thecontainer.

15. The structure of claim 11 wherein the means to concentrate the raysof light includes a concave reflector supported exteriorly of thecontainer and supported upon the wall thereof. 10

IRA E. MCCABE.

